In 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a mobile communication system, a discontinuous reception (DRX) is prescribed as an intermittent reception technique to reduce power consumption of a radio terminal. A radio terminal in a DRX state in a connected mode intermittently monitors a downlink control channel, based on DRX configuration information received from a base station. A cycle in which the downlink control channel is monitored is referred to as “DRX cycle”. Furthermore, monitoring duration arising in each DRX cycle is referred to as “On duration”.
In recent years, machine-type communication (MTC) in which a radio terminal performs communication without human intervention in a mobile communication system has attracted attention. From such a background, an ongoing discussion is a new introduction of an extended DRX cycle longer than a conventional DRX cycle to further reduce power consumption (for example, see Non Patent Document 1). The DRX using the extended DRX cycle is referred to as “extended DRX”.
Furthermore, the existing DRX includes a long DRX using a long DRX cycle and a short DRX using a short DRX cycle. When a DRX is configured to a radio terminal, in the 3GPP specifications, a long DRX is a mandatory function and a short DRX is an optional function.